1. Field of the Invention
The present invention relates to a signal transmission system for use in a camera.
2. Description of the Prior Art
In a camera adopting a central processing unit referred to as CPU made of a microcomputer and one or more IC (integrated circuit) chips for controlling the sequential operation of various peripheral units for a film winding operation, lens shifting operation for an automatic focusing control or the like, there are usually used data signals in a serial form for the communication between CPU and IC chips of the various peripheral equipment. However, because of the data signals being in a serial form it takes a very long time for the transmission of the data signals, so that there is a defect that a high speed data process is impossible, resulting in difficulty in high speed data processing for controlling the peripheral equipment. In case of adopting SLR (single lens reflex) system, data communication of CPU with various kinds of accessories attached to the camera is necessary. For example, in case a flash device is used in a position apart from the camera, because of using an extending cable between the camera and flash device, there occurs a delay of the data transmission and the data signals may not be transmitted correctly in case the clock pulses for controlling the data transmission are fast.
In personal computers, the transmission clock can be switched at the computer depending on the ability of a printer connected to the computers. However, the communication destination of one computer is limited to one position i.e., one printer, so that it is impossible to adapt this data transmission system to a camera having a plurality of data destinations. Also there is a commercially available one chip microcomputer of variable transmission speed, (M 50745 manufactured by Mitsubishi Electric Corporation, Japan) in which the data transmission speed can be changed by switching the transmission clock at the serial input and output port or I/O port of the microcomputer. However, a catalogue introducing the microcomputer does not mention about how to adapt it to a camera having a plurality of data designations.